Abstract: Qinghai Lake is located in the northeastern edge of the Tibetan—Qinghai Plateau．It is the largest saline lake in China．Due to uneven uplift of the plateau, some of the basins formed lakes in an isolated drainage system．The geochemistry of bedrocks affects the hydrological chemistry of drainage area and the physicochemical features of the Qinghai Lake．The main source of organic carbon is the ecological system surrounding the lake；Weathering of rocks also contributes to the carbon source in the lake．The chemistry of the Lake is heterogeneous in both vertical and horizontal dimensions；Changing of seasons also influences the hydrochemistry． These characteristics bring forth a unique microbiological ecology as well as a coupled carbon and metal cycling system． Enhanced concentrati0ns of Fe，SO42-, CO32-, Ca，Mg ions provide sufficient nutrients for the prosperity of a complex ecological system． Thisbiological cycling consequently provides sufficient chemicals for biomineralization． As has been surveyed, the lakeis of high diversity of algae，whose populations and community structures change seasonally． As a Dart 0f the evolution of the lake，the biological relics have been recorded as organic or inorganic biosignatures in the bottom sediments．Further study of the biological records and their relationship to the evolution of the local microbial ecology and cycling of carbon and other elements is expected to have important implications for climatic and environmental changes in the Tibetan—Qinghai P1ateau．Qinghai Lake